Method for making semiconducting single wall carbon nanotubes

ABSTRACT

A method for making semiconducting single walled carbon nanotubes (SWCNTs) includes providing a substrate. A single walled carbon nanotube film including metallic SWCNTs and semiconducting SWCNTs is located on the substrate. At least one electrode is located on the single walled carbon nanotube film and electrically connected with the single walled carbon nanotube film. A macromolecule material layer is located on the single walled carbon nanotube film to cover the single walled carbon nanotube film. The macromolecule material layer covering the metallic SWCNTs is removed by an electron beam bombardment method, to expose the metallic SWCNTs. The metallic SWCNTs and the macromolecule material layer covering the semiconducting SWCNTs are removed.

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201210075757.8, filed on Mar. 21, 2012 inthe China Intellectual Property Office. This application is related tocommonly-assigned application Ser. No. 13/798,789 entitled “METHOD FORMAKING SEMICONDUCTING CARBON NANOTUBES,” concurrently filed. Disclosuresof the above-identified applications are incorporated herein byreference.

BACKGROUND

1. Technical Field

The present application relates to a method for making semiconductingsingle walled carbon nanotubes.

2. Discussion of Related Art

Single walled carbon nanotubes (SWCNTs) may be metallic orsemiconducting, and may have varying diameters and lengths. Applicationsusing SWCNTs may be improved if SWCNTs of uniform conductivity, such asall semiconducting SWCNTs or all metallic SWCNTs, are provided.Accordingly, a method for making semiconducting SWCNTs is desired.

A method for making semiconducting SWCNTs involves destruction ofmetallic SWCNTs by electric current (See, Collin P. et al., Science,2001, 292, 706). A principle of this method is that semiconductingSWCNTs can be turn “off” by applying a gate voltage. It is possible toburn out metallic SWCNTs by application of a high source-drain voltagein the presence of oxygen. However, when a current flows through themetallic SWCNTs, Joule heat generated by the metallic SWCNTs mightinadvertently burn out the adjacent semiconducting SWCNTs.

What is needed, therefore, is to provide a method for makingsemiconducting SWCNTs that can overcome the above-described shortcomings

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a schematic process flow of one embodiment of a method formaking semiconducting SWCNTs.

FIG. 2 is an illustration of a growing device for making a single walledcarbon nanotube film.

FIG. 3 shows a scanning electron microscope image of the single walledcarbon nanotube film manufactured by the growing device of FIG. 2.

FIG. 4 is a schematic view of another embodiment of the single walledcarbon nanotube film according to FIG. 1.

FIG. 5 is a schematic view of one embodiment of an electrode located onone side of the single walled carbon nanotube film of FIG. 2.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

Referring to FIG. 1, a method for making semiconducting SWCNTs of oneembodiment includes steps of:

(S1), providing a substrate 10 having a first surface 102;

(S2), placing a single walled carbon nanotube film 12 on the firstsurface 102 of the substrate 10, wherein the single walled carbonnanotube film 12 includes a plurality of metallic SWCNTs 122 and aplurality of semiconducting SWCNTs 124;

(S3), applying a macromolecule material layer 14 on the single walledcarbon nanotube film 12 to cover each of the plurality of metallicSWCNTs 122 and each of the semiconducting SWCNTs 124, wherein themacromolecule material layer 14, the single walled carbon nanotube film12 and the substrate 10 form a compound;

(S4), exposing the plurality of metallic SWCNTs 122 by melting ordecomposing the macromolecule material layer 14 in an environment filledwith electromagnetic waves;

(S5), removing the plurality of metallic SWCNTs 122; and

(S6), removing the macromolecule material layer 14 to obtain theplurality of semiconducting SWCNTs 124.

In the step (S1), the substrate 10 can be a substantially flat andsmooth silicon substrate, such as a P-type silicon wafer, an N-typesilicon wafer or a silicon wafer formed with an oxidized layer thereon.The substrate 10 can also be made of polymer or quartz. The substrate 10has a high melting point, and the melting point of the substrate 10 canbe greater than or equal to 600° C. In the first embodiment, a P-typesilicon wafer is used as the substrate 10.

In the step (S2), the single walled carbon nanotube film 12 includes aplurality of SWCNTs including a plurality of metallic SWCNTs 122 and aplurality of semiconducting SWCNTs 124. A positional relationship of themetallic SWCNTs 122 and the semiconducting SWCNTs 124 is arbitrary. Theplurality of SWCNTs is parallel to a surface of the single walled carbonnanotube film 12 and the first surface 102 of the substrate 10. In thesingle walled carbon nanotube film 12, two adjacent SWCNTs are not incontact with each other, to prevent a heat of the metallic SWCNTs 122from burning out adjacent semiconducting SWCNTs 124. A distance betweentwo adjacent SWCNTs can be greater than or equal to 10 nanometers. Theplurality of SWCNTs can have the same length and be parallel to eachother. The plurality of SWCNTs can have different lengths and not beparallel to each other. In one embodiment, the plurality of SWCNTs hasthe same length and is parallel to each other, the distance between twoadjacent SWCNTs is 500 nanometers. A thickness of the single walledcarbon nanotube film 12 can be in a range from about 0.5 nanometers toabout 10 nanometers. In one embodiment, the thickness of the singlewalled carbon nanotube film 12 is in a range from about 0.5 nanometersto about 5 nanometers.

Referring to FIG. 2, a method for making the single walled carbonnanotube film 12 of one embodiment includes steps of:

(S21), providing a growing device 30 including a fixing supporter 310and a rotatable supporter 312;

(S22), providing a growing substrate 316 and the substrate 10, wherein acatalyst layer 318 is formed on a surface of the growing substrate 316;

(S23), placing the growing substrate 316 on the fixing supporter 310,and placing the substrate 10 on the rotatable supporter 312;

(S24), introducing a carbonaceous gas to grow a plurality of SWCNTsalong a gas flow direction;

(S25), stopping introducing the carbonaceous gas, the plurality ofSWCNTs formed on the first surface 102 of the substrate 10 is parallelto each other; and

(S26), changing the growing substrate 316, and the single walled carbonnanotube film 12 is formed on the first surface 102 of the substrate 10.

In the step (S21), the reacting room 304 has a gas inlet 306 and a gasoutlet 308. A rotatable supporter 312 disposes in the reacting room 304.A fixing supporter 310 disposed in the reacting room 304 is closer tothe gas inlet 306 than the rotatable supporter 312. A distance betweenthe rotatable supporter 312 and the fixing supporter 310 is less than 1micrometer. The rotatable supporter 312 is lower than the fixingsupporter 310. The rotatable supporter 312 can rotate in the horizontalplane arbitrarily.

In the step (S22), the catalyst layer 318 includes a layer ofmonodisperse catalyst. The method of forming the catalyst layer 318depends on the material of the monodisperse catalyst.

While the catalyst is made of iron (Fe), cobalt (Co), nickel (Ni), orany alloy thereof, the process of forming the catalyst layer 318 on thegrowing substrate 316 includes the following substeps of: (a1)depositing a layer of monodisperse catalyst on the growing substrate316; (a2) patterning the layer of monodisperse catalyst to form acatalyst layer 318 which is patterned. The method of depositing thecatalyst layer 318 is selected from the group comprising of physicalvapor deposition, chemical vapor deposition, coating and plating. Thethickness of the catalyst layer 318 approximately ranges from 1nanometer to 3 nanometers. Due to the thickness of the catalyst layer318 being small, the catalyst materials in the catalyst layer 318 formsa plurality of monodisperse catalyst particles.

If the catalyst layer 318 is made of monodisperse solution of metal ormetal-salt, the process of forming the catalyst layer 318 on the growingsubstrate 316 includes the following substeps of: (a1′) applying amonodisperse solution onto the surface of the growing substrate 316 toform a layer of monodisperse solution; (a2′) drying the monodispersesolution layer to form a catalyst layer 318. The step (a1′) can bereplaced by dipping the growing substrate 316 into the monodispersesolution. It could avoid the catalyst materials to gather together byusing monodisperse solution to form the catalyst layer 318. Therefore,the catalyst layer 318 includes a plurality of monodisperse catalystparticles. The monodisperse solution of metal-salt can be selected fromthe group comprising a solution of Fe(NO₃)₃ and water, solution of CuCl₂and water, solution of FeCl₃ and water, solution of Fe(NO₃)₃ andethanol, solution of CuCl₂ and ethanol, and solution of FeCl₃ andethanol. The monodisperse solution of metal is selected from the groupcomprising a solution of Fe—Mo and n-octane, solution of Fe—Co andn-octane, solution of Fe—Ru and n-octane, solution of Fe—Mo and hexane,solution of Fe—Co and hexane, solution of Fe—Ru and hexane, solution ofFe—Mo and ethanol, solution Fe—Co and ethanol, and solution of Fe—Ru andethanol. In one embodiment, the catalyst layer 318 is formed by asolution of Fe(NO₃)₃ and ethanol.

In the step (S23), while placing the growing substrate 316 on the fixingsupporter 310, it is necessary to make sure the catalyst layer 318 facesup. The growing substrate 316 and the substrate 10 are made of highmelting materials. The melting point of the growing substrate 316 andthe substrate 10 is above the growing temperature of the single walledcarbon nanotube film. The shape and area of the growing substrate 316and the substrate 10 is arbitrary.

The growing substrate 316 can be a rectangle. In one embodiment, thegrowing substrate 316 is a silicon strip. The length of the growingsubstrate 316 is 10 centimeters and the width of the growing substrate316 is 1 millimeter. The growing substrate 316 can be made by the stepsof forming a catalyst layer 318 on a large wafer, and then cutting thelarge wafer into a number of silicon strips of predetermined size. Thesubstrate 10 can be a square. The length of side of the substrate 10approximately ranges from 1 centimeter to 10 centimeters. Also, thesubstrate 10 can be a network, such as copper wire mesh. In oneembodiment, the substrate 10 is a 4-inch wafer.

The step (24) includes the following substeps of: (b1) introducing aprotective gas into the reacting room 304 to evacuate the air in thereacting room 304; (b2) heating the reacting room 304 up to growingtemperature of the SWCNTs; and (b3) introducing a carbonaceous gas togrow the SWCNTs.

In the step (b1), the protective gas is selected from the groupcomprising of nitrogen (N₂) gas and noble gas. In one embodiment, theprotective gas is argon (Ar) gas.

In the step (b2), the growing temperature of the SWCNTs rangesapproximately from 800 degrees to 1000 degrees. It is to be understoodthat the growing temperature varies with the carbonaceous gas. In oneembodiment, the carbonaceous gas is ethanol, so the growing temperatureof the SWCNTs ranges approximately from 850 degrees to 950 degrees. Ifthe carbonaceous gas were methane, the growing temperature of the SWCNTswould range approximately from 950 degrees to 1000 degrees.

In the step (b3), the carbonaceous gas is hydrocarbon with activechemical properties. The carbonaceous gas can be selected from the groupcomprising of ethanol, ethane, methane, and combinations thereof. In oneembodiment, the carbonaceous gas is ethanol or methane. The flux of thecarbonaceous gas ranges approximately from 5 to 100 milliliter perminute. An additional carrier gas such as hydrogen, can be alsointroduced into the reacting room 304 with the carbonaceous gas. Theflux ratio of the carbonaceous gas and the carrier gas rangesapproximately from 1:1 to 1:3.

After introducing the carbonaceous gas into the reacting room 304, itstarts to grow carbon nanotubes under the effect of the catalyst. Oneend (i.e., the root) of the carbon nanotubes is fixed on the growingsubstrate 316, and the other end (i.e., the top/free end) of the carbonnanotubes grow continuously. The density of the carbon nanotubes is lowdue to the catalyst layer 318 including a plurality of monodispersecatalyst grain. Therefore, a part of the carbon nanotubes grow intoSWCNTs. Because the fixing supporter 310 disposed in the reacting room304 is near the gas inlet 306, the SWCNTs float above the substrate 10with the roots of the SWCNTs still sticking on the growing substrate316, as the carbonaceous gas is continuously introduced into thereacting room 304. The mechanism of growing SWCNTs is called“kite-mechanism.” The length of the SWCNTs depends on the growing time.In one embodiment, the growing time approximately ranges from 10 minutesto 30 minutes. The length of the SWCNTs approximately ranges from 1centimeter to 30 centimeters.

In the step (S25), after cutting off the supply of the carbonaceous gasinto the reacting room 304, the SWCNTs stop growing and land on thesubstrate 10. The SWCNTs fall down onto the substrate 10 parallel andseparately due to the gravity and are allowed to cool. In order to avoidoxidation of the SWCNTs, the protective gas should be continuously fedinto the reacting room 304 until the temperature of the reacting room304 is cooled down to room temperature. Furthermore, the single walledcarbon nanotube film 12 is cut off from the growing substrate 316.

In the step (S26), changing the growing substrate 316 can be carried outby providing a new one of the growing substrate 316 with the catalystlayer 318 or recycling the original growing substrate 316. The originalgrowing substrate 316 is recycled by cleaning the original growingsubstrate 316 and forming a new catalyst layer 318 thereon. More SWCNTscan fall on to the first surface 102 of the substrate 10 to form thesingle walled carbon nanotube film 12 by repeating steps (S24) and (S25)as often as desired.

Referring to FIG. 3, the single walled carbon nanotube film 12 has aplurality of SWCNTs parallel to each other. The plurality of SWCNTs hasthe same length of 100 micrometers, the distance between two adjacentSWCNTs is 500 nanometers. The SWCNTs in the single walled carbonnanotube film 12 connect to each other by van der Waals attractive forcetherebetween, thus, the single walled carbon nanotube film 12 is afree-standing structure.

The term “free-standing” includes, but not limited to, the single walledcarbon nanotube film 12 that does not have to be supported by asubstrate. For example, the single walled carbon nanotube film 12 whichis free-standing can sustain the weight of itself when it is hoisted bya portion thereof without any significant damage to its structuralintegrity. So, if the single walled carbon nanotube film 12 which isfree-standing is placed between two separate supporters, a portion ofthe free-standing single walled carbon nanotube film 12, not in contactwith the two supporters, would be suspended between the two supportersand yet maintain film structural integrity.

It is understood, the single walled carbon nanotube film 12 can beformed by coating a solution of SWCNTs on the first surface 102 of thesubstrate 10. At the same time, the SWCNTs can have different lengthsand not be parallel to each other. It is necessary to make sure twoadjacent SWCNTs are not in contact with each other, as shown in FIG. 4.

In the step (S3), the macromolecule material layer 14 can enclose eachof the plurality of metallic SWCNTs and each of the plurality ofsemiconducting SWCNTs. The space between each two adjacent SWCNTs of theplurality of SWCNTs is filled with material of the macromoleculematerial layer 14. The macromolecule material layer 14 is formed bycoating a macromolecule solution or molten macromolecule material. Themacromolecule solution is formed by dissolving a macromolecule materialinto an organic solvent. The organic solvent can be ethanol, methanol,acetone, or chloroform. The molten macromolecule material is formed byheating the macromolecule material to a molten temperature of themacromolecule material. The macromolecule solution or the moltenmacromolecule material can have a viscosity greater than 1 Pa·s. Amelting point of the macromolecule material can be lower than or equalto 600° C., or a decomposing temperature of the macromolecule materialcan be lower than or equal to 600° C. In one embodiment, the meltingpoint of the macromolecule material is lower than or equal to 300° C.,or a decomposing temperature of the macromolecule material is lower thanor equal to 300° C. The macromolecule material can be phenolic resin(PF), polystyrene (PS), ethoxyline resin (EP), polyurethane (PU),polymethyl methacrylate. (PMMA), polycarbonate (PC), polyethyleneterephthalate (PET), or polyalkenamer.

The macromolecule solution or the molten macromolecule material can beuniformly coated on the surface of the single walled carbon nanotubefilm 12 by a spraying method, or a spin coating method. The surface ofthe single walled carbon nanotube film 12 away from the substrate 10 canbe immersed in the macromolecule solution. It is necessary to make surethe macromolecule material layer 14 cover each of the plurality ofSWCNTs. A thickness of the macromolecule material layer 14 is related tothe distance between two adjacent SWCNTs. The thickness of themacromolecule material layer 14 can be in a range from about 0.1micrometers to about 1 millimeter. In one embodiment, the macromoleculematerial is PMMA, and the organic solvent is methyl-phenoxide.

In the step (S4), the macromolecule material layer 14 barely absorbselectromagnetic wave energy. A heat capacity per unit area of themacromolecule material layer 14 is greater than the heat capacity perunit area of the single walled carbon nanotube film 12. Thesemiconducting SWCNTs 124 barely absorb the electromagnetic wave energy,but the metallic SWCNTs 122 can absorb the electromagnetic wave energyand generate heat. That is, a speed of absorbing the electromagneticwave energy of the metallic SWCNTs 122 is faster than the speed ofabsorbing the electromagnetic wave energy of the semiconducting SWCNTs124. Thus, after absorbing the electromagnetic wave energy, atemperature of the metallic SWCNTs 122 rises quickly. This temperatureincrease will heat the portions of the macromolecule material layer 14covering the metallic SWCNTs 122 until the macromolecule material layer14 is melted or decomposed. The metallic SWCNTs 122 are exposed becausethe portions of the macromolecule material layer 14 covering themetallic SWCNTs 122 is melted or decomposed.

At the same time, the heat generated by the metallic SWCNTs 122 can beabsorbed by the macromolecule material layer 14 and the substrate 10.Thus, the temperature of the single walled carbon nanotube film 12 canbe controlled to be under 700° C., and the single walled carbon nanotubefilm 12 will not burn.

The semiconducting SWCNTs 124 barely absorbs the electromagnetic waveenergy, so the temperature of the portion of the macromolecule materiallayer 14 covering the semiconducting SWCNTs 124 dose not rise. Theportions of the macromolecule material layer 14 covering thesemiconducting SWCNTs 124 are not melted or decomposed. Thus, thesemiconducting SWCNTs 124 are still covered by the macromoleculematerial layer 14.

In one embodiment, the thickness of the macromolecule material layer 14is less than the distance between two adjacent SWCNTs, in order toexpose the metallic SWCNTs 122 but not burn out their adjacentsemiconducting SWCNTs 124. In one embodiment, the thickness of themacromolecule material layer 14 is in a range from about 10 nanometersto about 500 nanometers, the temperature of the portions of themacromolecule material layer 14 covering the metallic SWCNTs 122 israised to 300 degrees.

A power of the electromagnetic waves can be in a range from about 300watts to about 2000 watts. A frequency of the electromagnetic waves canbe in a range from about 0.3 gigahertz to about 1×10⁶ gigahertz. Theelectromagnetic waves can be radio frequency, microwaves, near infrared,or far infrared. In one embodiment, the electromagnetic waves aremicrowaves. A power of the microwaves can be in a range from about 300watts to about 1500 watts. A frequency of the microwaves can be in arange from about 0.3 gigahertz to about 300 gigahertz. The compound iskept in a chamber filled with the microwaves from about 1 second toabout 600 seconds. In other embodiments, the compound is kept in thechamber filled with the microwaves from about 3 seconds to about 90seconds. The time period the compound is kept in the chamber filled withthe microwaves depends on the macromolecule material layer 14 and thepower of the microwaves. The higher the power of the microwaves, theshorter the time the chamber needs to be filled with the microwaves. Inone embodiment, the time is about 30 seconds.

The step (S4) can be carried out in a vacuum environment or in aspecific atmosphere of protective gases such as nitrogen gas or inertgases. A gas pressure of the environment is in a range from about 1×10⁻²Pascals to about 1×10⁻⁶ Pascals. The single walled carbon nanotube film12 can reach the temperature of about 900 degrees in the vacuumenvironment or in the specific atmosphere of protective gases.

In the step (S5), the metallic SWCNTs 122 can be removed by a reactiveion etching (RIE) method. A method of the RIE of one embodiment includessteps of:

(S51), disposing the macromolecule material layer 14, the single walledcarbon nanotube film 12 and the substrate 10 in a reactive ion etchingvacuum chamber;

(S52), introducing reactive gas into the reactive ion etching vacuumchamber; and

(S53), etching away the metallic SWCNTs 122 by reactive ions generatedby glow discharge of the reactive gas.

In the step (S52), the reactive gas can be oxygen, hydrogen, argon,ammonia, or CF₄. In one embodiment, the reactive gas is oxygen gas.

In the step (S53), during the etching process, the reactive ions etchaway the metallic SWCNTs 122. A power of the RIE system can be in arange from about 20 watts to about 300 watts. A flow rate of thereactive gas can be in a range from about 10 sccm to about 100 sccm. Anetching period can be in a range from about 5 seconds to about 10minutes. In one embodiment, the power of the RIE system is about 30watts, the flow rate of the reactive gas is about 50 sccm, and theetching period is in a range from about 15 seconds to about 1 minute.

In the step (S6), the macromolecule material layer 14 can be removed bya chemical reagent. The chemical reagent can be tetrahydrofuran,dichloroethane, chloroform, acetone, glacial acetic acid, dioxane,tetrahydrofuran, acetic ether, or toluene. In one embodiment, themacromolecule material layer 14 is immersed into the acetone to removethe macromolecule material layer 14, wherein the macromolecule materiallayer 14 is made of PMMA. Furthermore, the semiconducting SWCNTs 124located on the first surface 102 of the substrate 10 can be taken outfrom the chemical reagent and dried.

Referring to FIGS. 1 and 5, a method for making semiconducting SWCNTs ofanother embodiment includes steps of:

(S1), providing a substrate 10 having a first surface 102;

(S2), placing a single walled carbon nanotube film 12 on the firstsurface 102 of the substrate 10, wherein the single walled carbonnanotube film 12 includes a plurality of metallic SWCNTs 122 and aplurality of semiconducting SWCNTs 124;

(S3), applying at least one electrode 16 on one side of the singlewalled carbon nanotube film 12 and electrically connecting with thesingle walled carbon nanotube film 12;

(S4), forming a macromolecule material layer 14 on the single walledcarbon nanotube film 12 to cover each of the plurality of metallicSWCNTs 122 and each of the semiconducting SWCNTs 124;

(S5), exposing the plurality of metallic SWCNTs 122 by bombarding themacromolecule material layer 14 with an electron beam;

(S6), removing the plurality of metallic SWCNTs 122; and

(S7), removing the macromolecule material layer 14 to obtain theplurality of semiconducting SWCNTs 124.

The step (S1) where the melting point of the substrate 10 can bearbitrary.

In step (S2), two adjacent SWCNTs of the single walled carbon nanotubefilm 12 can be in contact with each other or be spaced from each other.The plurality of SWCNTs of the single walled carbon nanotube film 12 hasthe same length and be parallel to each other.

In the step (S3), the at least one electrode 16 can be located on oneside of the single walled carbon nanotube film 12. In one embodiment,two of the electrodes 16 are located on opposite two sides of the singlewalled carbon nanotube film 12. The at least one electrode 16 iselectrically connected to one end or two ends of the plurality ofSWCNTs.

The electrode 16 can be made of conductive material, such as metal,conductive polymer, conductive adhesive, metallic carbon nanotubes, orindium tin oxide. The shape and structure of the electrode 16 isarbitrary. The electrodes 16 can be made by a method such as screenprinting, chemical vapor deposition, or magnetron sputtering. In oneembodiment, the electrode 16 is formed concurrently by printingconductive silver paste. The conductive silver paste can include about50% to about 90% (by weight) of the metal powder, about 2% to about 10%(by weight) of the glass powder, and about 8% to about 40% (by weight)of the binder.

In the step (S4), the melting point of the macromolecule material layer14 can be arbitrary. The macromolecule material layer 14 can bepenetrated by a high-energy electron beam.

In the step (S5), an electron beam source is located above themacromolecule material layer 14, and an electric field is suppliedbetween the electron beam source and the macromolecule material layer14. The electron beam source can emit the high-energy electron beamincluding a plurality of electrons.

During the bombarding process, when the plurality of electrons from theelectron beam source reaches to the semiconducting SWCNTs 124, firstlythe semiconducting SWCNTs 124 will collect and gather the plurality ofelectrons. The plurality of electrons collected and gathered by thesemiconducting SWCNTs 124 can form a protective layer to protect thesemiconducting SWCNTs 124. Then when some electrons form the electronbeam source continue to reach to the semiconducting SWCNTs 124, theelectrons will be reflected by the protective layer to the metallicSWCNTs 122.

When the electrons from the electron beam source and reflected by theprotective layer reach to the metallic SWCNTs 122, the electrons will betransmitted to the electrode 16 along an axial direction of each of themetallic SWCNTs 122 in the electric field. In the process oftransmitting the electrons along the axial direction of each of themetallic SWCNTs 122 in the electric field, the portions of themacromolecule material layer 14 covering the metallic SWCNTs 122 will beetched, and the metallic SWCNTs 122 will be exposed. The semiconductingSWCNTs 124 are still covered by the macromolecule material layer 14.

Energy of the high-energy electron beam from the electron beam sourcecan be in a range from about 200 electron volts (eV) to about 200kiloelectron volts (KeV). Electron beam bombarding time can be in arange from about 5 seconds to about 10 minutes. In one embodiment, theenergy of the high-energy electron beam is in a range from about 500 eVto about 100 KeV, and the electron beam bombarding time is in a rangefrom about 30 seconds to about 5 minutes.

In summary, in the process of making the semiconducting SWCNTs 124 byabove-described methods, the metallic SWCNTs 122 can be completelyremoved, and the semiconducting SWCNTs 124 are not destroyed. Thus, thesemiconducting SWCNTs 124 have high purity. Moreover, the method formaking the semiconducting SWCNTs 124 is simple and can be mass producedin a large quantity.

It is to be understood that the above-described embodiment is intendedto illustrate rather than limit the disclosure. Variations may be madeto the embodiment without departing from the spirit of the disclosure asclaimed. The above-described embodiments are intended to illustrate thescope of the disclosure and not restricted to the scope of thedisclosure.

It is also to be understood that the above description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A semiconducting single walled carbon nanotubes(SWCNTs) making method comprising: placing a single walled carbonnanotube film on a first surface of a substrate, wherein the singlewalled carbon nanotube film comprises a plurality of SWCNTs comprisingmetallic SWCNTs and semiconducting SWCNTs; electrically connecting anelectrode with the single walled carbon nanotube film; applying amacromolecule material layer on the single walled carbon nanotube filmto cover the single walled carbon nanotube film; exposing the metallicSWCNTs by bombarding the macromolecule material layer with an electronbeam; removing the metallic SWCNTs; and removing the macromoleculematerial layer.
 2. The semiconducting SWCNTs making method of claim 1,wherein adjacent SWCNTs of the plurality of SWCNTs are not in contactwith each other, and a distance between the adjacent SWCNTs is greaterthan or equal to 10 nanometers.
 3. The semiconducting SWCNTs makingmethod of claim 1, wherein adjacent SWCNTs of the plurality of SWCNTsare in contact with each other.
 4. The semiconducting SWCNTs makingmethod of claim 1, wherein the plurality of SWCNTs has a same length andis parallelly spaced from each other.
 5. The semiconducting SWCNTsmaking method of claim 1, wherein the single walled carbon nanotube filmis a free-standing structure.
 6. The semiconducting SWCNTs making methodof claim 1, wherein the plurality of SWCNTs is parallel to a surface ofthe single walled carbon nanotube film and the first surface of thesubstrate.
 7. The semiconducting SWCNTs making method of claim 1,wherein the electrically connecting the electrode with the single walledcarbon nanotube film comprises contacting the electrode with one side ofthe single walled carbon nanotube film.
 8. The semiconducting SWCNTsmaking method of claim 1, wherein the electrically connecting theelectrode with the single walled carbon nanotube film comprisescontacting a first electrode with a first side of the single walledcarbon nanotube film and contacting a second electrode with a secondside of the single walled carbon nanotube film opposite to the firstside.
 9. The semiconducting SWCNTs making method of claim 1, wherein theelectrically connecting the electrode with the single walled carbonnanotube film comprises electrically connecting a first electrode to afirst end of each of the plurality of SWCNTs and connecting a secondelectrode to a second end of each of the plurality of SWCNTs opposite tothe first end.
 10. The semiconducting SWCNTs making method of claim 1,wherein a thickness of the macromolecule material layer is in a rangefrom about 0.1 micrometers to about 1 millimeter.
 11. The semiconductingSWCNTs making method of claim 1, wherein the applying the macromoleculematerial layer on the single walled carbon nanotube film comprisescoating a macromolecule solution or molten macromolecule material. 12.The semiconducting SWCNTs making method of claim 11, wherein themacromolecule material is penetrated by the electron beam.
 13. Thesemiconducting SWCNTs making method of claim 12, wherein energy of theelectron beam is in a range from about 200 electron volts to about 200kiloelectron volts.
 14. The semiconducting SWCNTs making method of claim1, wherein the macromolecule material layer encloses each of themetallic SWCNTs and each of the semiconducting SWCNTs.
 15. Thesemiconducting SWCNTs making method of claim 1, wherein spaces betweenadjacent SWCNTs of the plurality of SWCNTs are filled with material ofthe macromolecule material layer.
 16. The semiconducting SWCNTs makingmethod of claim 1, wherein the removing the metallic SWCNTs comprisessteps of: disposing the treated compound in a reactive ion etchingvacuum chamber; introducing reactive gas into the reactive ion etchingvacuum chamber; and etching away the metallic SWCNTs by reactive ionsgenerated by glow discharge of the reactive gas.
 17. The semiconductingSWCNTs making method of claim 1, wherein the removing the macromoleculematerial layer comprises treating the macromolecule material layer by achemical reagent.
 18. A semiconducting single walled carbon nanotubes(SWCNTs) making method comprising: placing a single walled carbonnanotube film on a first surface of a substrate, wherein the singlewalled carbon nanotube film comprises a plurality of SWCNTs comprisingmetallic SWCNTs and semiconducting SWCNTs, wherein the plurality ofSWCNTs is parallel to each other; electrically connecting an electrodewith the single walled carbon nanotube film; applying a macromoleculematerial layer on the single walled carbon nanotube film to enclose eachof the metallic SWCNTs and each of the semiconducting SWCNTs; exposingthe metallic SWCNTs by bombarding the macromolecule material layer withan electron beam; etching away the metallic SWCNTs; and removing themacromolecule material layer.
 19. The semiconducting SWCNTs makingmethod of claim 18, wherein a distance between adjacent SWCNTs of theplurality of SWCNTs is greater than or equal to 10 nanometers.
 20. Thesemiconducting SWCNTs making method of claim 18, wherein spaces betweenadjacent SWCNTs of the plurality of SWCNTs are filled with material ofthe macromolecule material layer.